1. Field of Invention
The present invention relates to an apparatus and method for estimating a state of charge (SOC) in a battery, and more particularly to an apparatus and method for estimating an SOC in a battery, using fusion type soft computing.
2. Description of Related Art
In general, a state of charge (SOC) in a battery has a nonlinear characteristic. Hence, it is difficult to accurately detect the battery SOC in practice. As a result, the detection of the battery SOC depends on its estimation method.
Examples of a conventional estimation method of the battery SOC include an amp-hour (Ah) counting method, an open circuit voltage (OCV) measuring method, a battery impedance measuring method, and so on.
The Ah counting method is for detecting the SOC by detecting a real capacity of the battery. However, the Ah counting method is greatly influenced by errors or precision of sensors detecting the real capacity, thereby having a great error.
The OCV measuring method is for reading out open voltage of the battery in an idle state, and estimating an SOC from the read open voltage. This method has problems in that it can be used only in the idle state, and it is greatly influenced by external factors such as temperature.
The battery impedance measuring method is for estimating an SOC of the battery from an impedance measurement value of the battery. This method has a problem in that the precision of an estimation value is lowered because it is greatly influenced by temperature.
Mobile phones, laptop computers etc. used in a low C-rate environment do not require accurate detection of the battery SOC in view of their characteristics. In these products, the battery SOC is readily estimated by the Ah counting method, the OCV measuring method, or so on. Here, the term C-rate refers to magnitude of the peak current that can be output in a moment.
However, in the case of hybrid electrical vehicles (HEVs), electrical vehicles (EVs) etc. used in a high C-rate environment, accurate information on the battery SOC is required like the fuel gauge of an ordinary vehicle, while a degree of non-linearity of the battery SOC is enhanced. Hence, the conventional methods for estimating the battery SOC have difficulty in estimating the battery SOC in these products.